Do you know the rules used? I'm curious as to why they were stopping or is it because they moved outside of the last circle?

Sport sambo rules. Standing escapes for armbars, leg locks. quick ground time (1 minute after sub attempts). No chokes. Out of bounds resets the match. 4, 2, or 1 point based on throw. 4 or 2 point based on a pin. Total victory if the thrower is standing and the uke lands flat on his back.

We already know this was not the world university games and it was in Buffalo, not Montreal.

But, regarding the video, the closest thing to what Sonnon describes would be the armbar at about 2 minutes. There is a quick break before they go back to work and the ref looks like he his checking Sonnon's arms when they return. That was a very quick stoppage on the standing escape IMO (one of the things I don't like about sport sambo). But, the armbar looked very tight and Sonnon was visibly pacing and seemed upset before the camera cuts and action starts again.

It does look like Sonnon's hand was still gripping the kurtka during the armbar...which is why it is so tight I think. Hard to tell in this vid, but that is what it looks like. Nevertheless, his arm does not look like it "shattered" as he says in his first account:

Unfortunately, my opponent was the better athlete that day, and landed me in an arm-bar. I refused to tap out, since submitting would have cost the USA Sambo Team more team points. In his grip, my arm shattered under the precision force of his technique, as a squelched my pain since making any noise while in a joint lock means that you submit.

It is also not the flying armbar and verbal tap out Zurab recalled in his phone conversation with Matt.

In Sonnon's second description he says:

My concealment of the injury led to avascular necrosis in my scaphoid: a condition that locked my hand in vice-like pain unable to hold anything. When your sport involves being able to grip a man and throw him to the ground, the inability to hold anything is career ending.

In this description, Sonnon describes an injury to his scaphoid (Avascular necrosis). Which would make more sense if his hand were trapped in the kurtka as it seems to look like. This is an injury of the wrist, not the arm and is most common when people fall on an outstretched hand:

He also states that his hiding the injury during the match led to the avascular necrosis. This is not really possible as avascular necrosis is a disease process which evolves over time (no blood flow to the bone = bone death). It certainly would not have developed in a matter of minutes I suspect (maybe a Dr. could confirm this?). A fructure of the scaphoid could of course happen in a match.

I would also add that Sonnon did not seem to be trying to conceal anything or even favor the injured arm/wrist during the remaining 4 minutes of the match. In fact he often uses it as his dominant gripping hand. I would also add that there were many falls of his which were on that hand which may have also caused such a fracture of the wrist.

Props to Sonnon for keeping his cool in such an outclassed situation. I have been there...it aint easy. But those descriptions just don't match the video.

This is not really possible as avascular necrosis is a disease process which evolves over time (no blood flow to the bone = bone death). It certainly would not have developed in a matter of minutes I suspect (maybe a Dr. could confirm this?).

Avascular necrosis does take many months to occur and obviously could not have developed in the match. However, the likelihood for development of avascular necrosis depends on the severity of the fracture and the degree of displacement of the bone fragments.

Concealing the injury and continuing to fight could have resulted in a more serious fracture and more complete displacement of the pieces which later lead to avascular necrosis which could have been avoided if the broken bone was not subjected to additional stress.

I am sure concealing such an injury could hurt the situation. However, is it realisitic to think that he concealed an injury which "shattered" his arm as he said? And is is safe to assume the extra 3 minutes or so made a huge difference?

According to his own account, he knew it was broken and hid it...because he felt it "shatter". He hid the break for a matter of 3 or so minutes. Would those extra minutes make a big difference IF he were to have saught medical attention afterwards as he should have? I wonder how long it was before he saw a doctor about his "shattered" arm (or wrist depending on which of his stories we listen to). I suspect the time it took to get medical attention (which surely was longer than the few minutes he hid the injury) would have been more of a factor. But, that is assuming he actually broke something, actually hid the inujury, and actually went to the doctor in a timely fashion.

Here is another more likely possible version of the story. He had a small fracture, did not know about it, never went to the doctor in a timely manner, and had avascular necrosis as a result of the delay in medical attention.

His story simply does not add up to me...especially after watching the video.